Control units for internal combustion engines acquire signals from sensors such as lambda sensors, temperature sensors, a mass airflow sensor, angle of rotation sensors, cylinder pressure sensors, knock sensors and driver's intent sensors, process them, and control actuators on the internal combustion engine such as fuel metering devices, electrical ignition devices, and an air supply metering device. The objective is to make power of the internal combustion engine available according to the driver's intent. But an additional role of the control unit is to achieve correct functioning of the internal combustion engine in regard to low-emission combustion, and when necessary to provide diagnostic data which permit controlling the function of the internal combustion engine. The functions of the control unit may be implemented as an electronic circuit or as a program sequence, or as a combination of the two.
To control the function of an internal combustion engine, it is customary to connect the controller via a standardized interface to an external test device, a so-called diagnostic tester or diagnostics device, via which data may be sent to the control unit in order to set operating conditions of the internal combustion engine selectively, and via which data may be read out from the control unit, processed and displayed. This makes it possible to perform a comprehensive test of the functions of the internal combustion engine, the control unit, the connected sensors, and the actuators during a stop in the repair shop.
During such a checkup, the external test device sends a query for a particular type of value to the control unit, which returns the actual value of the value type. For example, the actual value of the signal of a lambda sensor may be queried in this way. If multiple time-sequential values are needed, a query is sent to the external test device for each value to be transmitted. The method described results in a minimum cycle time, which is one of the factors determined by the data exchange between the test device and the control unit and which limits the maximum frequency of the queries. Furthermore, the cycle time is not necessarily constant, so that periodic queries, for example queries coupled with the rotational speed of the internal combustion engine, are exacerbated.
U.S. Pat. No. 6,601,015 B1 describes a method an internal combustion engine having a number of cyclically moving pistons for driving a land vehicle and a control unit having data memories for the internal combustion engine, the controller controlling the internal combustion engine by periodically monitoring a number of performance parameters, a first starting event being established at which a first number of values which represent at least part of the performance parameters of the internal combustion engine are stored in the memory at a first predefined frequency, and a second starting event being established at which a second number of values are stored in the memory at a second predefined frequency, the values representing at least part of the performance parameters of the internal combustion engine, and the first predefined frequency being settable by the first starting event, the second predefined frequency being settable by the second starting event, and the first and second frequencies may be predefined differently.